DIMM (dual in-line memory module) technology has random access memory (RAM) integrated circuits (ICs) mounted on a printed circuit board (PCB). Various types of DIMMs exist. DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) DIMM technology has a parallel external interface. Fully buffered DIMM or FB-DIMM technology has a serial external interface.
FB-DIMM technology employs an Advanced Memory Buffer (AMB) having a serial connection to a memory controller, and a parallel connection to dynamic random access memory (DRAM). The AMB on each FB-DIMM translates the communication in serial point-to-point link protocol received from the memory host controller to DDR2 or DDR3 SDRAM parallel protocol transmitted to the DRAMs as read, write, refresh, etc. operations within the DIMM.
FB-DIMM architecture uses a southbound (SB) high speed link to send command and data information from the memory host controller to the AMB on each FB-DIMM and a northbound (NB) high speed link to transfer data from the AMBs on the FB-DIMMs to the memory host controller. The AMBs transfer read/write command and data to the DRAMs on each FB-DIMM. The high speed serial link interface between the memory host controller and the FB-DIMMs employs frames having cyclic redundancy check (CRC) with the data to transfer the data. The interface between each AMB and the DRAMs uses the DDR2 or DDR3 SDRAM parallel protocol to transfer data, address, and control.